Solenoids as described in the beginning are well known in the art. For example, they serve as operating or servo parts for driving valves or the like. The field of application of the solenoids of this type is also very large. For example, they are used in vehicles or aircrafts. Costs and weight, respectively, of the used components have to be taken into consideration in these applications.
In the state of the art constructions of the above-mentioned solenoids are known that can be used when the working pressure occurring in the armature housing is explicitly high (for example of 200 bar and more). Of course, solenoids of this type have to be configured sufficiently pressure-resistant to work reliably and to be leakage-free.
For cost efficient manufacture of the casing, housing single components of the solenoid (coil, connection parts, plugs etc.), state-of-the-art manufacturing methods are employed. Thus, for example, the casing is configured as powder injection molded part. The advantage of using this production method to provide a casing, also called MIM (metal injection molding) or metal powder injection molding, is the fact that by means of these manufacturing methods rather complicated geometrical dimensions can be produced in the casing in a single manufacturing step, if necessary even without additional metal-cutting machining Thus it is convenient, to surround the armature housing with a casing wall that is manufactured in one piece with the further casing.
It has to be taken into consideration, that high pressure prevails in the armature housing that act, of course, also on the walls of the armature housing as well. Behind the casing wall, that seals the armature housing, the coil body is arranged carrying a multitude of windings of wire flown through by electricity. In order to optimize the efficiency of the solenoid of this type, the wall thickness of all casing parts, also the wall thickness of the casing wall surrounding the armature housing is minimized as far as possible. In the bottom and top area of the armature housing, respectively of course, the casing wall surrounding the armature housing joins the rest of the casing wall. The configuration in one piece in this area is advantageous for highly leakproof area. However, in this transition area suitable reinforcements are required at the casing wall surrounding the armature housing, as here the shearing forces or the notching effect is considerable in particular with the very high pressure and the resulting pressure forces.
It is therefore known in this transition area on the side opposite of the armature housing, to provide a reinforcement that is, for example, a rounding or a flute between the casing wall delimiting the solenoid and the casing wall surrounding the armature housing.
Therefore, this reinforcement is in the area where also the coil body is arranged.
The coil body carries windings of the electrically conducting wire, the coil itself is wound automatically. Therefore, the coil is manufactured optimized as ideal cylinder. When compared with modifications without reinforcements, the arrangement of a reinforcement (rounding or flute) consumes construction space in axial direction of the coil in the area where the coil is mounted.
In order to achieve the same mechanic and/or magnetic effect of the high pressure-proof solenoid, the solenoid altogether has to be configured somewhat larger. This results in costs and additional weight which is undesirable in particular applications.